A display device capable of presenting different kinds of video on one screen when seen from different angles has been proposed. Such a display device is called a dual view display device. For example, an in-vehicle dual view display device presents video for car navigation or presents no video to a driver's seat side while presenting another video such as a movie and a television program to a passenger's seat side, thereby ensuring safe driving and providing various kinds of video for fellow passengers.
Here, Patent Document 1 describes a light control element outputting light in a first polarization state to a first angular range and outputting light in a second polarization state to a second angular range and a dual view display including the same.
FIG. 16 is a schematic view showing the configuration of the conventional dual view display described in Patent Document 1. In FIG. 16, a vertical direction is referred to as an x-direction, a horizontal direction as a y-direction and a front-back direction as a z-direction.
As shown in FIG. 16, a first optical control element 503, a second optical control element 504, a switchable half-wavelength plate 505 and a linear polarizer 506 are arranged between a back light 501 and a transmissive image display panel 502. The switchable half-wavelength plate 505 is arranged so as to have an optical axis of 45° with respect to a transmission axis of the linear polarizer 506.
As indicated by the solid arrows L, the first optical control element 503 transmits polarized light in the vertical direction (hereinafter referred to as x-polarized light) to a narrow angular range with about +30°, for example, as a center with respect to an axis of the display in the z-direction, and does not absorb polarized light in the horizontal direction (hereinafter referred to as y-polarized light). As indicated by the solid arrows R, the second optical control element 504 transmits the y-polarized light to a narrow angular range with about −30°, for example, as a center with respect to the axis of the display in the z-direction, and does not absorb the x-polarized light. The switchable half-wavelength plate 505 does not affect the polarized light passing therethrough when turned off, and rotates the polarized light by 90° when turned on. The linear polarizer 506 with its transmission axis arranged in the y-direction absorbs the x-polarized light and transmits the y-polarized light.
In one display mode of the display, the switchable half-wavelength plate 505 is turned off and does not affect the polarized light passing therethrough. The first optical control element 503 does not affect the y-polarized light. Thus, the y-polarized light from the back light 501 passes through the first optical control element 503 to be led in the direction of the arrows R by the second optical control element 504. The y-polarized light passes through the linear polarizer 506 to be output toward a viewer 520. Meanwhile, the x-polarized light that is led in the direction of the arrow L by the first optical control element 503 is absorbed by the linear polarizer 506. Accordingly, the viewer 520 can see video displayed on the display panel 502 and a viewer 510 sees the dark display panel 502.
In another display mode of the display, the switchable half-wavelength plate 505 is turned on and rotates the polarized light by 90°. The second optical control element 504 does not affect the x-polarized light. The x-polarized light from the back light 501 is led in the direction of the arrows L by the first optical control element 503 to pass through the second optical control element 504. The x-polarized light is converted into the y-polarized light by the switchable half-wavelength plate 505. Thus, the y-polarized light passes through the linear polarizer 506 to be output toward the viewer 510. Meanwhile, the y-polarized light led in the direction of the arrows R by the second optical control element 504 is converted into the x-polarized light by the switchable half-wavelength plate 505 to be absorbed by the linear polarizer 506. Accordingly, the viewer 510 can see video displayed on the display panel 502 and the viewer 520 sees the dark display panel 502.
When video is presented for each of the viewer 510 and the viewer 520, the switchable half-wavelength plate 505 is switched between an on state and an off state at high speed. Video for the viewer 520 is displayed during a period where the switchable half-wavelength plate 505 is turned off and video for the viewer 510 is displayed during a period where the switchable half-wavelength plate 505 is turned on. In this manner, video displayed on the display panel 502 is switched in synchronization with a switching operation of the switchable half-wavelength plate 505.
[Patent Document 1] JP 2005-78093 A